Thought-controlled arm helps amputees

LONDON – A thought-controlled prosthetic arm is being developed by Max Ortiz Catalan of Chalmers University (Gothenburg, Sweden). This research project is using a titanium implant system that anchors the prosthesis directly to the skeleton through osseointegration.

Since the 1960s, amputees have been able to use prostheses controlled by electrical impulses in the muscles. However, the functionality is limited because they are difficult to control.

Standard socket prostheses, which are attached to the body using a socket tightly fitted on the amputated stump, are so uncomfortable and limiting that only 50 percent of arm amputees are willing to use one at all, according to Ortiz Catalan, an industrial doctoral student at Chalmers.

"Our technology helps amputees to control an artificial limb, in much the same way as their own biological hand or arm, via the person's own nerves and remaining muscles. This is a huge benefit for both the individual and to society," said Ortiz Catalan.

In this project, the researchers are planning to implant the electrodes directly on the nerves and remaining muscles. Since the electrodes are closer to the source and the body acts as protection, the bio-electric signals become much more stable than skin-mounted electrodes.

The electrical impulses from the nerves in the arm stump are captured by a neural interface, which sends them to the prostheses through the titanium implant. These are then decoded to allow the patient to control the prosthesis using his or her own thoughts.

An amputee patient's prosthesis can be
controlled by brain signals. The signals are transferred via the
nerves through the arm stump and captured by electrodes. These will then
transmit the signals through a titanium implant to be
decoded by the prosthetic arm to control specific joints and actions. The prosthesis is anchored directly to the
skeleton by a process known as osseointegration. Source: Intregrum

In existing prostheses, amputees use only visual or auditory feedback. With the new method, patients receive feedback as the electrodes stimulate the neural pathways to the patient's brain, in the same way as the physiological system. This means that the patient can control his or her prosthesis in a more natural and intuitive way.

"If the first operations this winter are successful, we will be the first research group in the world to make ‘thought-controlled prostheses’ a reality for patients to use in their daily activities, and not only inside research labs," said Ortiz Catalan.

The research project Natural control of artificial limbs through an osseointegrated implant is being conducted by means of interdisciplinary
cooperation between the Chalmers University of Technology, Sahlgrenska
University Hospital and Integrum AB.